1. Field of the Invention
The present invention relates to a substrate processing apparatus and method of manufacturing a semiconductor device, and more particularly to the effective utilization thereof in a substrate processing technology in which, in a process for manufacturing a semiconductor device, a thermochemical reaction is utilized to administer a desired processing such as the fabrication of an oxide film or metal film on a substrate such as a semiconductor wafer (hereinafter also referred to as a wafer).
2. Description of the Related Art
In a process for manufacturing a semiconductor device, vertical-type semiconductor manufacturing apparatuses are sometimes employed as substrate processing apparatuses for fabricating an oxide film or metal film on a wafer.
Conventional vertical-type semiconductor manufacturing apparatuses of this type comprise a processing furnace configured from a reaction vessel and a heater in which a gas is introduced into the heated reaction vessel while being exhausted therefrom. Various methods are employed for introducing the gas into the reaction vessel.
For example, in the vertical-type semiconductor manufacturing apparatus shown in FIG. 18, a cylindrical reaction tube 2 serving as an outer tube configured from a heat-resistant material such as quartz glass is disposed roughly perpendicularly on a manifold 5 constituted from, for example, a metal material such as stainless steel. A cylindrical tube 3 serving as an inner tube is provided on the inner side of the reaction tube 2. A port 4 for holding a plurality of wafers W is provided in the inner side of the cylindrical tube 3. A gas introduction inlet 6 and an exhaust outlet 7 are provided in the manifold 5. In addition, a heater 1 is provided to surround the outer circumference of the reaction tube 2, the interior of the reaction tube 2 being able to be thermally processed thereby to a predetermined temperature. The reaction vessel is constituted from the aforementioned reaction tube 2, cylindrical tube 3 and manifold 5.
In a process of film formation, a predetermined film formation gas is introduced as indicated by the arrows through the introduction inlet 6 provided in the manifold 5 into the interior of the reaction tube 2 maintained to a predetermined pressure. The gas introduced from below the reaction tube 2 into the interior of the reaction tube is exhausted above the reaction tube 2 by way of a wafer processing space 10 and, after passing through a cylindrical space formed between the reaction tube 2 and the cylindrical tube 3, is exhausted from the exhaust outlet 7 provided in the manifold 5. By provision of the introduction inlet 6 in the manifold 5 in the manufacturing apparatus shown in FIG. 18 in this way, a film formation gas is introduced from below the wafer processing space 10 and exhausted thereabove.
In addition, while the vertical-type semiconductor manufacturing apparatus shown in FIG. 19 has the same basic configuration as the apparatus shown in FIG. 18, the following points of difference exist therebetween. For the purpose of extending the introduction inlet 6 to the wafer processing space 10, a plurality of gas nozzles 16 of different length are provided upright from the manifold 5 into the wafer processing space 10. As shown by the arrows, a film formation gas is introduced through apex portions of the gas nozzles 16 located to the side of the wafers W, and exhausted therebelow through the gas exhaust outlet 7 (for example, see Japanese Unexamined Patent Application Publication No. 2000-68214).
In addition, while the vertical-type semiconductor apparatus shown in FIG. 20 has the same basic configuration as the apparatus shown in FIG. 18, the following points of different exist therebetween. For the purpose of extending the introduction inlet 6 to the wafer processing space 10, a gas nozzle 26 is provided upright from the manifold 5. A large number of holes opposing the plurality of wafers W are provided in the gas nozzle 26, a film formation gas being introduced from the side of the wafers W and exhausted therebelow through the gas exhaust outlet 7 as shown by the arrows.
If the size of the diameters of the large number of holes provided in the gas nozzle 26 are the same, the flow rate of the film formation gas through these holes cannot be made uniform due to the gas pressure difference between holes provided in the lower part (gas upstream side) and the holes provided in the upper part (gas downstream side). Thereupon, in order to ensure uniformity of the flow rate of the film formation gas using a gas nozzle of this kind, the size of the diameter of the holes between the lower and upper parts is made different.
In addition, the reaction vessel of the vertical-type semiconductor manufacturing apparatus shown in FIG. 21 is a single tube configuration constituted from the reaction tube 2 alone, and does not comprise either a cylindrical tube or a manifold. A gas nozzle 36 that communicates with the introduction inlet 6 is provided along the outer side wall of the reaction tube 2 from below the reaction tube 2 to a ceiling portion of the reaction tube 2, a film formation gas being supplied from above the wafer processing space 10 and exhausted therebelow through the gas exhaust outlet 7 as shown by the arrows.
The following various problems are inherent to the conventional vertical-type semiconductor manufacturing apparatuses as described above.
For example, there is a problem inherent to the apparatus shown in FIG. 18 in that, because the film formation gas is introduced from below and exhausted thereabove, the film formation gas is less likely to flow to the center of the wafers W and, accordingly, differences in film thickness between the center and outer circumferential portions of the wafers are generated and the wafer in-plane film thickness uniformity is affected. There is a further problem inherent thereto in that, comparing the wafers W of positions in the lower part and the upper part of the wafer processing space 10, film formation differences between wafers located in the upper part and those in the lower part are generated due to consumption of the film formation gas occurring at the lower part and, accordingly, the wafers of the lower part are formed thicker and the wafer in-plane film thickness uniformity is affected.
In addition, in the apparatus shown in FIG. 19, even though the in-plane and interwafer film thickness uniformity are by and large satisfactory, the necessity for a plurality of gas nozzles of differing length translates to poor maintenance characteristics. In addition, because the gas nozzles 16 are provided in the wafer processing space 10, reaction product attaches to and accumulates thereon. This attachment and accumulation of a reaction product is particularly marked in the process for the formation of, for example, a Si3N4 film. There is an additional problem in that, if the film formation conditions are altered, in most instances the changes in the film formation conditions cannot be accommodated without altering length and the number of the gas nozzles 16, while not altering the type of gas nozzles 16 restricts the conditions at which a film is able to be formed.
There is a problem inherent to the apparatus shown in FIG. 20 in that, because the gas nozzle 26 is provided in the wafer processing space 10, reaction product attaches to and accumulates thereon. More specifically, this problem resides in the necessity for a maintenance operation to be performed on the holes of the gas nozzle 26 when a reaction product attaches to and accumulates thereon. For example, when the attachment and accumulation of a reaction product is likely to occur such as in the process for the formation of a Si3N4 film, the holes block quickly and a maintenance operation on these holes must be frequently performed. There is an additional problem in that, if the film formation conditions are altered, the gas nozzle type must be altered in order to alter the holes, and not altering the type of gas nozzle restricts the conditions in which film formation is possible. A further problem resides in the increase in the size of the holes of the gas nozzle 26 caused by an etching processing performed to clean the reaction product and, accordingly, the need for the gas nozzle to be replaced to control the hole size.
In addition, there is a problem inherent to the apparatus shown in FIG. 21 in that the in-plane and interwafer film thickness uniformity are affected in the same way as described for the apparatus of FIG. 18.
A problem inherent to conventional substrate processing apparatuses in which a gas is introduced from below a reaction tube and exhausted thereabove as described above resides in the gas not being able to pass properly across the substrates and, in turn, the in-plane and intersubstrate film thickness uniformity being unable to be improved. An additional problem inherent to conventional substrate processing apparatuses in which a gas is supplied via a gas nozzle from the side of a reaction tube and exhausted thereabove resides in the in-plane and interwafer film thickness uniformity being unable to be improved without the gas inlet tube being frequently maintained and replaced.
With the problems of the conventional art described above in mind, it is an object of the present invention to provide a substrate processing apparatus and method of manufacturing a semiconductor device that, eliminating the need for the gas supply pipe to be frequently maintained and replaced, affords improved wafer in-plane and interwafer film thickness uniformity of a plurality of wafers on which a film is simultaneously formed.